1. Field of the Invention
The present invention relates to an image forming apparatus that forms an image on a recording medium, such as a copier, a printer, a facsimile, and a multifunction product.
2. Description of the Related Art
In an image forming apparatus such as a copier, a printer, a facsimile, and a multifunction product (MFP), an image is formed by conveying a recording medium such as a sheet on a conveying path, so that a sheet may be jammed during a conveyance of the sheet. Because the sheet jam is basically cleared by a user, it is indispensable to make a jam processing easier for a user.
Japanese Patent Application Laid-open No. 2003-186371 discloses an image forming apparatus in which a cover unit that includes a transfer carrying belt unit, a guiding plate, and a registration roller on a driven side is arranged to be openable with respect to a body of the apparatus so that a sheet conveying path from a sheet feeding roller to a portion just before a fixing unit is exposed. The cover unit is supported by a swing shaft in a swingable manner with respect to the body. The cover unit needs to be detachable from the body for a maintenance or a component replacement.
FIG. 17 is a perspective view of a swing shaft supporting portion for supporting a detachable cover unit. An oval-shaped shaft 200 with an oval section that is short in an axial direction is arranged on each inner wall of both side plates of a body of an image forming apparatus. The cover unit includes bearing members 210 each having a cutout portion 211 from which a small diameter portion 201 of the oval-shaped shaft 200 can escape. The oval-shaped shaft 200 is inserted into the bearing member 210 by allowing the small diameter portion 201 to pass through the cutout portion 211. In this state, a large diameter portion 202 of the oval-shaped shaft 200 is supported by the bearing member 210. The configuration makes it possible for the cover unit to swing with respect to the body. In addition, by appropriately positioning the cutout portion 211 with respect to the small diameter portion 201 and moving the cover unit in a direction in which the small diameter portion 201 can escape, the cover unit can be taken out of the body.
However, when such bearing configuration is used, a positioning accuracy of the cover unit is degraded because each end of the cover unit is independently supported by the oval-shaped shaft 200, which may adversely affect a sheet conveyance or an image transfer. Specifically, a misalignment occurs in a shaft line of a conveying unit in the cover unit with respect to a conveying unit in the body that conveys sheets in cooperation with the conveying unit in the cover unit, which may cause jamming or skewing of sheets.